1. Field of the Invention
This invention relates to a means for printing on both sides of a paper document, and, more particularly, to printing automatically on both sides of a check at a point of sale terminal with a single print mechanism.
2. Description of the Related Art
In continuing attempts to provide more efficient and convenient service to customers, many retailers have begun to use "point of sale check printers" to reduce the time required for a customer to fill out and sign a check. Such a printer automatically enters the date, amount of purchase, and the name of the retail establishment, to which payment is being made, in the corresponding spaces of a check provided by the customer. The signature line is left blank, for the customer to sign after he has been presented with the printed check.
Another form of printing performed on a check by the retailer is the printing of franking information on the reverse side of the check. This information generally indicates that the check is for deposit only or that it is to be deposited only to a particular account. While it is not necessary to perform this printing operation at the point of sale, many retail establishments have a policy of printing this information, with a rubber stamp if necessary, at the point of sale, reducing the possibility of unrecoverable losses from checks stolen without franking information, which are later stamped or printed with forged information. It is therefore desirable for a point of sale check printer to be able to print on both sides of the check, with the amount of the check and the name of the retail establishment being printed on the front side of the check, and with the franking information being printed on the reverse side.
One method for printing on both sides of a check simply places an additional burden on the cashier using the point of sale terminal. The check is inserted into the printer for printing on a first side, removed, turned over, and then inserted into the printer for printing on the second side. While this method is the simplest in terms of the hardware required, the additional operations required to be performed by the cashier increase the time required for a transaction while also reducing the chance that the printing operation will be performed correctly. U.S. Pat. No. 5,553,817 provides an example of a printer configured for this type of operation, being capable of printing in either direction, across the width of a document, as needed for printing the franking information, or along its length, as required for printing information on the front side of a check. What is needed in this printer is a way for moving the document so that printing can occur on both sides without removal and reinsertion.
Some printers, such as the printer described in U.S. Pat. No. 5,558,449, provide for printing on both sides of a sheet of paper with two separate print mechanisms, operating on opposite sides of the sheet of paper. However, this approach naturally increases the complexity of the printer mechanism while tending to reduce its reliability. U.S. Pat. No. 4,561,352 describes apparatus for printing on either side of a document, but not on both sides, in a single pass of the document through the apparatus. This apparatus is configured to print on envelopes, with the operator viewing the information on the front of the document, and with the apparatus then printing information keyed by the operator, such as a bar code representing the zip code or a routing code, on either the front or the back of the envelope. The print module includes two parallel document paths and a print head between the document paths. The print module is manually positioned between a first position, in which first document path is aligned with input and output paths of the apparatus, with the print head facing the first document path, and a second position, in which the second document path is aligned with the input and output paths of the apparatus, with the print head facing the second document path. A rack moving with the first and second document paths causes the print head to rotate between positions facing each of the document paths as the print module is moved.
The apparatus of U.S. Pat. No. 4,561,352 is not well suited for many applications, such as the printing of checks at a point of sale terminal, because a means is needed for moving a document between the two document paths to print on both sides of the document in a single pass through the apparatus, and because the apparatus is too large to fit in available space.
U.S. Pat. No. 4,932,798 describes a thermal transfer printer for printing on both sides of a document, which is carried past a print head while lying against a partial circumference of a print roller. In a first printing operation, a document fed from an input stack is printed on a first side and pulled through a 180-degree angle in contact with the print roller to be driven along a sheet seating surface. In a second printing operation, the document is fed from the sheet seating surface to be printed on the second side as it is again pulled through a 180-degree angle in contact with the print roller. A deflector plate is lowered so that, as the second printing operation is being completed, the document is fed into an output tray instead of being driven along the sheet seating surface.
U.S. Pat. No. 5,677,722 describes a thermal transfer printer capable of printing on both sides of a document. The printer includes first and second transferring rollers, first and second guide paths, and a paper-ejection path. The document is repositioned for printing on the reverse side, after the front side is completely printed by moving the document backward around a loop, with the document being driven through a 180-degree angle before it is again moved past the print head.
U.S. Pat. No. 5,746,526 describes a printer having a paper path feeding paper from a hopper along a "U"-shaped transport path formed of a first linear path, a curved path, and a second linear path. The print head prints on a front surface of the paper as it moves along the first linear path. Then the print head withdraws to a position adjacent the second linear path, from which the print head prints on the back surface of the paper.
U.S. Pat. No. 5,865,547 describes a print head and check flipper subassembly having a removable flipper cartridge to allow printing on both sides of a check or other document in one continuous operation. A check is fed downward, between a print head and platen, with printing occurring on a first side of the check, and into a loop within the flipper cartridge. The check continues around the loop, and is driven out of the loop, having been reversed front to back by being driven through a 180-degree angle in the loop. The check is fed upward between the print head and platen, with printing occurring on a second side of the check, and outward through the slot into which it has been inserted. This patent also describes the use of a Magnetic Ink Character Recognition (MICR) reader to read the characters extending along the lower edge of the check to determine the customer's bank and his account number.
A problem with the apparatus of U.S. Pat. Nos. 4,932,798, 5,677,722, 5,746,526 and 5,865,547 arises from the fact that the document must be driven through a 180-degree angle in a relatively tight loop before printing on the reverse side. Moving a document, such as a check, through such a large angle increases the chance that the document may become distorted, damaged, or jammed within the document path during the printing process. For example, when a document is driven through such a large angle, if one of the document edges extending along the document path moves at a faster speed than the opposite such document edge, the document becomes angularly misaligned in a manner which may cause information subsequently printed on the document to be misaligned and which may cause a paper jam or damage to the document. What is needed is a method for printing on both sides of a document while reducing the angle through which the document is bent as it travels through the document path.